The present invention relates to steered continuous wave Doppler ultrasound imaging.
Steered continuous wave Doppler imaging is provided using one-dimensional arrays. Dedicated transmit and receive apertures are used on the array, so coaxial cables and associated elements may be electrically isolated to avoid interference. The steered continuous wave Doppler receive beamformer is typically analog to provide large dynamic range and sensitivity. The data output by the steered continuous wave receive beamformer is used to generate a spectral Doppler image. A graph of velocities as a function of time is generated. For each given time, a range of velocities are highlighted. The highlighted velocities are modulated as a function of the associated energy. The range of velocities and associated energies at a given steer direction is displayed as a function of time as a moving graph.
The velocity information represents velocities towards and away from the transducer. Where blood flow is at an angle to the scan line, the actual velocity may differ. Various techniques are provided for angle correcting velocity information for two-dimensional imaging. For example, the user inputs an indication of the direction of flow within a two-dimensional image. The angle information is used to determine an actual velocity. As another example, the ultrasound system automatically acquires data at each spatial location from different angles and uses the angles and associated velocities to determine an actual velocity values. The angle information is used to determine an actual velocity. For two-dimensional imaging, the angle is applied to velocities at a plurality of locations in an image representing a scan region at a given time.
However, techniques applicable to one-dimensional arrays and two-dimensional imaging may not apply to steered continuous wave imaging using a two-dimensional array capable of three-dimensional imaging. Two dimensional arrays typically include hundreds or thousands of elements, such as an order of magnitude of 10 or more than one-dimensional arrays. Providing sufficient dynamic range and avoiding cross-talk may increase complexity and cost. Since circuitry may be provided within a transducer probe for each of the elements, the cost of providing sufficient dynamic range is increased for steered continuous wave imaging as compared to Doppler imaging using pulse waves.